Method and Arrangement for Transmitting and Receiving RF Signals Through Various Radio Interfaces of Communication Systems

ABSTRACT

A method and arrangement for transmitting and receiving RF signals, associated with different radio interfaces of communication systems, employ a direct conversion based transceiver which substantially comprises one receive signal branch and one transmit signal branch. Mixing frequencies of the different systems are generated by a single common by use of an output frequency divider in combination with the synthesizer, and by use of filtering corresponding to a system channel bandwidth by means of a controllable low-pass filter operating at baseband frequency.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. application Ser. No.14/272,191, filed May 7, 2014, which is a continuation of U.S.application Ser. No. 13/614,272, filed Sep. 13, 2012, which is acontinuation of U.S. application Ser. No. 12/136,465, filed Jun. 10,2008, which is a continuation of U.S. application Ser. No. 09/856,746,filed May 24, 2001 (issued as U.S. Pat. No. 7,415,247 on Aug. 19, 2008),which is a U.S. national stage of PCT/FI99/00974, filed Nov. 25, 1999,which is based on and claims priority to Finnish application no. 982559,filed Nov. 26, 1998, all incorporated by reference herein.

The invention relates to a method and arrangement for transmitting andreceiving RF signals associated with various radio interfaces ofcommunication systems. The invention finds particular utility intransceivers of general-purpose mobile stations.

Mobile communication systems are developing and expanding rapidly whichhas led to a situation in which there are in many areas systemscomplying with several different standards. This has brought about aneed for mobile stations that can be used in more than one system. Goodexamples are the digital systems called GSM (Global System for Mobilecommunications) and DCS (Digital Cellular System), which operate ondifferent frequency bands but have otherwise similar radio interfaces.In addition, the modulation, multiplexing and coding schemes used may bedifferent. The systems mentioned above use the time division multipleaccess (TDMA) method; other methods include the frequency divisionmultiple access (FDMA) and code division multiple access (CDMA).

One possible way of making a mobile station capable of operating inmultiple systems is to have in the mobile station completely separatesignal paths for each system. This, however, would lead to anunreasonable increase in the mobile station size and manufacturingcosts. Therefore, the goal is to design a mobile station in which thedifferences relating to the radio interfaces of the various systemscould be largely dealt with by means of programming, instead of havingseparate signal processing paths.

It is known e.g. from patent application document EP 653851 atransceiver arrangement using one local oscillator the frequency ofwhich falls between the lower operating frequency band and the higheroperating frequency band such that one and the same intermediatefrequency (IF) can be used for both operating frequency bands. However,the disadvantage of such a solution is that the necessary IF stages makethe implementation rather complex, and the manufacturing costs of thedevice will be high because of the great number of components.Furthermore, the IF stages require filters in order to eliminatespurious responses and spurious emissions. In addition, channelfiltering at the intermediate frequency sets great demands on the IFfilters.

In a direct-conversion, or zero-IF, receiver the radio-frequency (RF)signal is directly converted into baseband without any intermediatefrequencies. Since no IF stages are needed, the receiver requires only afew components, therefore being an advantageous solution forgeneral-purpose mobile stations which have multiple signal branches fordifferent systems. To aid in understanding the problems relating to thedirect conversion technique and prior art it is next described in moredetail a prior-art solution.

FIG. 1 shows a direct conversion based arrangement for realizing a dualfrequency band transceiver, known from the Finnish Patent document FI100286. Depending on the receive frequency band, a RF signal received byan antenna is coupled by means of switch 104 either to a first receivebranch (DCS) or second receive branch (GSM).

If the received signal is in the DCS frequency band, it is conducted tobandpass filter 106, low-noise amplifier (LNA) 108 and bandpass filter110. After that the signal is brought to block 112 which produces signalcomponents having a 90-degree phase difference. The in-phase component Iand quadrature component Q are further conducted by means of switches114 and 134 to mixers 116 and 136. The mixers get their mixing signalsfrom a DCS synthesizer 140 the frequency of which corresponds to thereceived carrier frequency so that the mixing produces the in-phase andquadrature components of the complex baseband signal. The basebandsignal is further processed in the receive (RX) signal processing unit,block 139.

If the signal received is a USM signal, switch 104 directs the receivedsignal to the GSM branch which comprises, connected in series bandpassfilter 126, low-noise amplifier 128, bandpass filter 130 and phaseshifter 132 which generates two signals with a mutual phase differenceof 90 degrees. The signals are further conducted by means of switches114 and 134 to mixers 116 and 136 where the mixing frequency is nowdetermined by a signal coming from the GSM synthesizer 150 via switch161. The signals produced by the mixers are further conducted to thebaseband RX signal processing unit 139.

The DCS synthesizer comprises in a known manner a phase-locked loop(PLL) which includes a voltage-controlled oscillator (VCO) 141 theoutput signal of which is amplified at amplifier 146 thus producing thesynthesizer output signal. The frequency of the signal from oscillator141 is divided by an integer Y in divider 142 and the resulting signalis conducted to phase comparator 43. Similarly, the frequency of thesignal generated by reference oscillator 158 is divided by an integer Xin divider 144 and conducted to phase comparator 143. The phasecomparator produces a signal proportional to the phase difference ofsaid two input signals, which signal is conducted to a low-pass filter(LPF) 145 producing a filtered signal that controls thevoltage-controlled oscillator 141 The phase-locked loop described aboveoperates in a known manner in which the output frequency of thesynthesizer becomes locked to the frequency coming to the phasecomparator from the reference frequency branch. The output frequency iscontrolled by varying the divisor Y.

The GSM synthesizer 150 comprises a voltage-controlled oscillator 150,amplifier 156, dividers 152 and 154, phase comparator 153 and a low-passfilter 155. The GSM synthesizer operates like the DCS synthesizerdescribed above, but the output frequency of the GSM synthesizercorresponds to GSM frequency bands.

In the transmitter part, a baseband complex transmit (TX) signal isprocessed in a TX signal processing unit wherefrom the in-phase andquadrature components of the signal are conducted to mixers 162 and 182that produce a carrier-frequency signal by multiplying the input signalby the mixing signal. If the transmission is at the DCS frequency,switch 161 selects the DCS synthesizer's output signal as the mixingsignal. The carrier-frequency signal is conducted through switch 164 tothe DCS branch where a 90-degree phase shift is first produced betweenthe in-phase component and quadrature component, and the resultingsignals are then summed, block 166. The resulting DCS signal isconducted to bandpass filter 168, amplifier 170, and bandpass filter172. The RF signal thus produced is further conducted to the antenna 102via switch 180.

If the transmission is at the GSM frequency, the output signal of theGSM synthesizer is used as the mixing signal. The resultingcarrier-frequency signal is conducted to the GSM branch in which it isprocessed in the same manner as in the DCS branch blocks 186, 188, 190and 192. The RF signal thus produced is conducted to the antenna 102 viaswitch 180. One and the same antenna 102 can be used in bothtransmission and reception if the TX and RX circuits are coupled to theantenna through a duplex filter, for example. If the apparatus isdesigned to operate in two or more frequency bands, it needs separatefilters for each frequency band.

The circuit arrangement described above has, however, somedisadvantages. First, separate carrier-frequency signal branches in thereceiver and m the transmitter add to the complexity, size andmanufacturing costs of the transceiver. Second, each operating frequencyband needs a separate synthesizer of its own.

An object of the invention is to provide a simple solution for realizinga programmable transceiver operating in a plurality of systems in such amanner that the aforementioned disadvantages related to the prior artcan be avoided.

In the direct conversion based transceiver according to the inventionsignal processing can be performed using one and the same signalprocessing line regardless of the system. This is achieved using thesignal processing steps set forth below.

The method according to the invention for processing signals receivedfrom different radio interfaces of communication systems ischaracterized in that it comprises steps in which

-   -   a carrier-frequency signal is received from a radio interface,    -   the carrier-frequency signal is bandpass-filtered,    -   the filtered carrier-frequency signal is amplified,    -   an RX mixing signal at the receive frequency is generated,    -   a complex baseband signal is generated from the received        carrier-frequency signal by mixing it with the RX mixing signal,    -   the baseband signal generated is low-pass-filtered,    -   the baseband signal generated is amplified,    -   the baseband signal is converted digital, and    -   the baseband signal converted digital is processed to produce an        information signal encoded and modulated into the received        signal.

The method according to the invention for processing signals transmittedto different radio interfaces of communication systems is characterizedin that it comprises steps in which

-   -   a digital baseband quadrature signal is generated on the basis        of the information signal to be transmitted,    -   the digital baseband signal is converted analog,    -   a TX mixing signal at the transmit frequency is generated,    -   a carrier-frequency transmission signal is generated from the        baseband signal by mixing it with the TX mixing signal,    -   the carrier-frequency signal generated is amplified, and    -   the transmission signal is sent to the radio interface.

The direct-conversion receiver according to the invention operating atdifferent interfaces of communication systems is characterized in thatit comprises

-   -   antenna means for receiving a radio-frequency signal,    -   bandpass filter for filtering a carrier-frequency signal,    -   first RX amplifier for amplifying the filtered carrier-frequency        signal,    -   means for generating an RX mixing signal at the receive        frequency,    -   mixing means for generating a complex baseband signal from the        received signal using the RX mixing signal,    -   low-pass filter for filtering the baseband signal,    -   second amplifier for amplifying the baseband signal,    -   analog-to-digital converter for converting the baseband signal        digital, and    -   means for processing the baseband signal converted digital to        produce an information signal encoded and modulated into the        received signal.

The direct-conversion transmitter according to the invention operatingat different radio interfaces of communication systems is characterizedin that it comprises

-   -   means for generating a digital baseband quadrature signal on the        basis of the information signal to be transmitted,    -   digital-to-analog converter for converting the baseband        transmission signal analog,    -   synthesizer for generating a TX mixing signal at the transmit        frequency,    -   mixing means for producing a signal at the carrier frequency        from the baseband transmission signal using the TX mixing        signal,    -   TX amplifier for amplifying the signal at the carrier frequency,        and    -   antenna means for transmitting the amplified transmission signal        at the carrier frequency.

Other preferred embodiments of the invention are described in thedependent claims.

In the present invention, signal band limiting is advantageouslyperformed at the baseband frequency so that there is no need for “steep”filters and, therefore, system-specific filter lines. Filtering can thusbe performed as low-pass filtering using a filter with a controllablecut-off frequency. This way, it is possible to completely avoid separatesystem-specific channel filtering circuits.

To enable the generation of mixing frequencies of the differentoperating frequency bands by one and the same synthesizer it isadvantageously used frequency division of the synthesizer output signal.If the synthesizer's operating frequency is set higher than thefrequencies used in the systems, it is possible to generate, inconjunction with the synthesizer frequency division, two mixing signalswith a 90-degree phase difference, thus avoiding the need for phaseshifters on the signal line and achieving a good phase accuracy.

Using the solution according to the invention it is possible to realizea general-purpose transceiver which is considerably simpler and moreeconomical to manufacture than prior-art solutions. The circuitarrangement according to the invention requires only one TX signalbranch and one RX signal branch. Moreover, one and the same synthesizermay be used to generate the mixing signals. Furthermore, there is noneed for channel filters operating at the radio frequency. Therefore,the circuitry can be easily integrated. Since the invention involvesonly a few components, the advantages of the transceiver according tothe invention include small size and low power consumption.

The invention will now be described in more detail with reference to theaccompanying drawing wherein

FIG. 1 shows a block diagram of a dual-band direct-conversiontransceiver according to the prior art,

FIG. 2 shows in the form of block diagram a solution according to theinvention for a direct-conversion transceiver operating in multiplesystems.

FIG. 1 was already discussed in conjunction with the description of theprior art. Next, a transceiver according to the invention will bedescribed, referring to FIG. 2.

FIG. 2 shows in the form of block diagram a transceiver according to theinvention. A RF signal received through an antenna is conducted viamatching circuits 1 to controllable bandpass filters 2. The matchingcircuits 1 may advantageously be controllable (AX) with respect to theoperating frequency band. A controllable bandpass filter 2 may beadvantageously realized using a plurality of bandpass filters so thatthe RF signal is conducted via switch elements controlled by a controlsignal FX1 from the matching circuit 1 to the bandpass filter thatcorresponds to the selected operating frequency band. The bandpassfilter may also be realized so as to be adjustable and tuneable by meansof programming. The bandpass filtered carrier-frequency signal isfurther conducted to a low-noise amplifier 4, the gain of which isadvantageously controllable. The control signal is marked GX1 in thedrawing. In addition to amplifier 4, it is also possible to haveintegrated amplifiers in connection with the bandpass filters.

The signal is then conducted to a mixer 5 in which the carrier-frequencysignal is mixed with an RX mixing signal at the receive frequency toproduce a baseband quadrature signal. The RX mixing signal isadvantageously generated by a synthesizer 10 the output signal frequencyof which is divided by a divider 11 so as to correspond to the selectedreceive frequency. The synthesizer 10 operates in a similar manner asthe synthesizers depicted in FIG. 1. Thus it comprises avoltage-controlled oscillator VCO which produces an output signal. Thefrequency of the VCO output signal is divided by S1 in a divider in thephase-locked loop PLL. The resulting signal is conducted to a firstinput of a phase comparator in the phase-locked loop. Similarly, thefrequency of a signal generated by a reference oscillator in thephase-locked loop PLL is divided by an integer and conducted to a secondinput of the phase comparator. The phase comparator produces a signalwhich is proportional to the phase difference of the two input signalsand conducted to a low-pass filter, and the filtered signal thencontrols the voltage-controlled oscillator VCO. The output frequency iscontrolled by varying the divisor S1.

The synthesizer output signal is divided in divider 11 by N1 so that theRX mixing signal corresponds to the selected receive frequency band. Theoutput frequency of the synthesizer may be e.g. in the 4-GHz band, sothat with 2-GHz systems the synthesizer output frequency is divided bytwo, and with 1-GHz systems it is divided by four (N1). This way,systems operating in the 1-GHz and 2-GHz bands can be covered with asynthesizer the operating frequency band of which is narrow with respectto the operating frequency.

To produce a quadrature baseband signal the mixer needs two mixingsignals with a phase shift of 90 degrees. Phase-shifted components maybe produced by a phase shifter in connection with the mixer or they maybe produced as quotients generated already in the frequency divider 11,thus achieving an accurate phase difference. Therefore, it isadvantageous to use a synthesizer operating frequency which is amultiple of the highest system frequency.

The in-phase component 1 and quadrature component Q from the mixer 5 arefurther conducted to low-pass filters 6. The higher cut-off frequency ofthe low-pass filters is advantageously controllable with control signalFX3. Thus the filtering can be performed at a bandwidth corresponding tothe selected radio interface, and since the filtering is performed atbaseband, it is easy to get the filtering function steep. Also, nostrict demands are set on the bandpass filtering (2) of the RF signal.

The baseband signal is further conducted to a gain control block 7 whichpossibly includes an offset voltage correction block. On the other hand,considering the broad bandwidth of the CDMA system, the offset voltagecan easily be removed by high-pass filtering. The amplifieradvantageously realizes automatic gain control (AGC). Finally, thesignal is convened digital in an analog-to-digital converter 8, and thedigital baseband signal is further processed in a digital signalprocessor (DSP) 9. Channel filtering may also be performed digitally inthe DSP, whereby the low-pass filtering of the baseband signal may beperformed using a fixed cut-off frequency. Then, however, the dynamicsof the analog-to-digital converter must be considerably better.

In the transmitter part, a quadrature baseband signal is first digitallygenerated in block 9 on the basis of the information signal to be sent.The components of the digital signal are converted analog bydigital-to-analog converters 14, whereafter the analog signals arelow-pass filtered by low-pass filters 15. Advantageously, the cutofffrequency of the low-pass filters can be controlled with control signalFX4 so as to correspond to the specifications of the selected radiointerface.

A TX mixing signal at the carrier frequency is generated by asynthesizer 13 and divider 12. The synthesizer 13 operates in a similarmanner as the synthesizer 10 in the receiver pan. Moreover, thesynthesizers may share a reference oscillator. The frequency of thesynthesizer output signal is controlled with control signal S2 withinthe synthesizer's operating frequency range. The frequency of the outputsignal from synthesizer 13 is divided in divider 12 so as to correspondto the selected transmission frequency band. Components phase-shifted by90 degrees are generated from the TX mixing signal in order to performcomplex mixing in mixer 16. The phase-shifted components may begenerated in the same way as in the receiver part.

The signal at the carrier frequency is then amplified in an amplifier17, the gain of which is advantageously controllable in order to set thetransmission power and realize automatic gain control (AGC). The controlsignal is marked GX3 in FIG. 2. The signal is then conducted to a poweramplifier 18. The operating frequency band of the power amplifier isadvantageously selectable with control signal BX. This can be achievede.g. such that the amplifier comprises partly separate signal lines forthe different operating frequency bands.

The RF signal generated is filtered by a bandpass filter 3. The passband of the bandpass filter is advantageously controllable with controlsignal FX2. This can be realized in the same way as in the receiverpart. The receiver and transmitter part filters 2 and 3 areadvantageously realized in duplex filter pairs for each transmit-receivefrequency band associated with a given system. The filters mayadvantageously be surface acoustic wave (SAW) or bulk acoustic wave(BAW) filters so that several filters with their switches may beattached to one component.

The control signals in the mobile station transceiver according to FIG.2 are preferably generated in a control block of the mobile stationwhich advantageously comprises a processing unit such as amicroprocessor. The control block generates the signal on the basis of asystem switch instruction input from the keypad of the mobile station,for example. System selection may be e.g. menu-based so that the desiredsystem is selected by choosing it from a displayed menu by pressing acertain key on the keypad. The control block then generates the controlsignals that correspond to the selected system. The system switchinstruction may also come via the mobile communication system in such amanner that data received from the system may include a system switchinstruction on the basis of which the control block performs the systemswitch. Advantageously, a control program is stored in a memory unitused by the control block, which control program monitors the receiveddata and, as it detects a system switch instruction in the data, givesthe control block an instruction to set the control signals into statesaccording to the selection instruction.

The implementation of the blocks described above is not illustrated inmore detail as the blocks can be realized on the basis of theinformation disclosed above, applying the usual know-how of a personskilled in the art.

Above it was described embodiments of the solution according to theinvention. Naturally, the principle according to the invention may bemodified within the scope of the invention as defined by the claimsappended hereto, e.g. as regards implementation details and fields ofapplication. It is especially noteworthy that the solution according tothe invention may be well applied to communication systems other thanthe mobile communication systems mentioned above. Apart from thecellular radio interface proper, the solution may be used to realizee.g. a GPS receiver for the location of a mobile station or otherapparatus. Furthermore, the operating frequencies mentioned are given byway of example only, and the implementation of the invention is in noway restricted to them.

It is also noteworthy that the solution according to the invention maybe applied to all current coding techniques such as the narrow-band FDMA(Frequency Division Multiple Access) and TDMA (Time Division MultipleAccess), as well as the broadband CDMA (Code Division Multiple Access)technique. In addition, the solution according to the invention may beused to realize an FM (Frequency Modulation) receiver.

Below is a table listing some of the so-called second generation mobilecommunication systems to which the present invention may be applied. Thetable shows the most important radio interface related characteristicsof the systems.

CELLULAR SYSTEM DECT PHS GSM Global Digital Personal System for PDCPersonal European Handy IS-95 US Mobile Digital Cordless Phone AMPSIS-54/136 CDMA Communications DCS 1800 Cellular Telephone System RXFREQ. (MHz) 869-894 869-894 869-894 935-960 1805-1880 810-826, 1880-19001895-1918 1429-1453 TX FREQ. (MHz) 824-849 824-849 824-849 890-9151710-1785 940-956 1880-1900 1895-1918 1477-1501 RF BANDWIDTH 25 MHz 25MHz  25 MHz  25 MHz  75 MHz 16 MHz, 24 MHz   20 MHz  23 MHz MULTIPLEACCESS FDMA TDMA/ CDMA/ TDMA/ TDMA/ TDMA/ TDMA/ TDMA/ METHOD FDMA FDMAFDMA FDMA FDMA FDMA FDMA DUPLEX METHOD FDD FDD FDD FDD FDD FDD TDD TDDNUMBER OF 832 832, 3 users/ 20, 798 users/ 124, 8 users/ 374, 8 users/1600, 3 users/ 10, 12 users/ 300, 4 users/ CHANNELS channel channelchannel channel channel channel channel CHANNEL SPACING 30 kHz 30 kHz1250 kHz 200 kHz 200 kHz 25 kHz 1.728 MHz 300 kHz MODULATION FM π/4QPSK/ GMSK 0.3 GMSK 0.3 π/4 GFSK 0.3 π/4 DQPSK OQPSK Gaussian GaussianDQPSK Gaussian DQPSK filter filter filter

Below is another table listing some of the so-called third generationmobile communication systems to which the present invention may beapplied. The table shows the most important radio interface relatedcharacteristics of the system.

CELLULAR SYSTEM WCDMA RX FREQ. (MHz) 2110-2170 1900-1920 TX FREQ. (MHz)1920-1980 1900-1920 MULTIPLE ACCESS METHOD CDMA TDMA DUPLEX METHOD FDDTDD CHANNEL SPACING 5 MHz 5 MHz MODULATION QPSK CHANNEL BIT RATE 144kb/s in rural outdoor, 500 kb/s in urban outdoor and up to 2 Mb/s inindoor

1. A direct-conversion transceiver capable of operating with differentradio interfaces including a first radio interface conforming to a codedivision multiple access (CDMA) system and a second radio interfaceconforming to a time division multiple access (TDMA) system, comprising:a first controllable bandpass filter configured to filter a receivedsignal according to a control signal that selects one of a plurality ofpassbands corresponding to one of the different radio interfaces,wherein the first controllable bandpass filter has a signal path commonto both the first radio interface and the second radio interface; alow-noise amplifier configured to amplify the filtered received signalaccording to a control signal that controls an amount of gain, whereinthe low-noise amplifier has a signal path common to both the first radiointerface and the second radio interface; a first programmablesynthesizer configured to generate a first mixing signal according to acontrol signal corresponding to the selected one radio interface,wherein the first programmable synthesizer has a signal path common toboth the first radio interface and the second radio interface; a firstfrequency divider coupled to the first programmable synthesizer andconfigured to divide a frequency of the first mixing signal by two toprovide a first divided frequency signal according to a control signalcorresponding to the selected one radio interface; a first mixer coupledto the low-noise amplifier and configured to mix the amplified andfiltered received signal with the first divided mixing signal to producea first baseband quadrature signal, wherein the first mixer has a signalpath common to both the first radio interface and the second radiointerface and wherein the first mixer produces the first basedbandquadrature signal on the basis of two 90-degree phase-shifted componentsproduced from the first frequency divider and is operable to processeither a TDMA signal or a CDMA signal; a first low-pass filter coupledto the first mixer and configured to low-pass filter the first basebandquadrature signal according to a control signal corresponding to theselected one radio interface, wherein the first low-pass filter has asignal path common to both the first radio interface and the secondradio interface and is operable to process either a TDMA signal or aCDMA signal; a first gain-controlled amplifier coupled to the firstlow-pass filter and configured to provide gain-controlled amplificationof the first low-pass filtered baseband quadrature signal, wherein thefirst gain-controlled amplifier has a signal path common to both thefirst radio interface and the second radio interface and is operable toprocess either a TDMA signal or a CDMA signal; an analog-to-digitalconverter coupled to the first gain-controlled amplifier and configuredto convert to digital form an output of the first gain-controlledamplifier; a digital signal processor configured to receive digitaloutput from the analog-to-digital converter and to further process saiddigital output; a digital-to-analog converter coupled to the digitalsignal processor and configured to receive a second baseband quadraturesignal therefrom and to provide analog output signals; a second low-passfilter coupled to the digital-to-analog converter and configured tolow-pass filter the analog output signals from the digital-to-analogconverter according to a control signal corresponding to the selectedone radio interface, wherein the second low-pass filter has a signalpath common to both the first radio interface and the second radiointerface and is operable to process either a TDMA signal or a CDMAsignal; a second programmable synthesizer configured to generate asecond mixing signal according to a control signal corresponding to theselected one radio interface, wherein the second programmablesynthesizer has a signal path common to both the first radio interfaceand the second radio interface; a second frequency divider coupled tothe second programmable synthesizer and configured to divide a frequencyof the second mixing signal by two to provide a second divided frequencysignal according to a control signal corresponding to the selected oneradio interface; a second mixer coupled to the second low-pass filterand configured to mix signals from the second low-pass filter and thesecond frequency divider to produce a carrier-frequency transmissionsignal, wherein the second mixer has a signal path common to both thefirst radio interface and the second radio interface and wherein thesecond mixer produces the carrier-frequency transmission signal on thebasis of two 90-degree phase-shifted components produced from the secondfrequency divider and is operable to process either a TDMA signal or aCDMA signal; a second gain-controlled amplifier coupled to the secondmixer and configured to control gain according to a control signalcorresponding to the selected one radio interface, wherein the secondgain-controlled amplifier has a signal path common to both the firstradio interface and the second radio interface and is operable toprocess either a TDMA signal or a CDMA signal; a power amplifier coupledto the second gain-controlled amplifier and configured to produce anamplified output using a frequency band determined on the basis of acontrol signal corresponding to the selected one radio interface,wherein the power amplifier has a signal path common to both the firstradio interface and the second radio interface; a second controllablebandpass filter configured to filter an output of the power amplifieraccording to a control signal that selects one of a plurality ofpassbands corresponding to the selected one radio interface, wherein thesecond controllable bandpass filter has a signal path common to both thefirst radio interface and the second radio interface; and amicroprocessor configured to generate one or more control signals tocause selection of the selected radio interface.